Dam Safety & Security

Reclamation issues contracts for several dams needing repair

The Bureau of Reclamation has awarded contracts for dam repair work in three states that will cost more than $55 million.

Red Willow Dam, Nebraska

Reclamation has awarded a $15.3 million contract to SEMA Construction Inc. for rehabilitation of Red Willow Dam in Nebraska, which has been a concern since discovery of a sinkhole and cracking through the embankment in 2009. This discovery prompted Reclamation to draw down Hugh Butler Lake, an 86,630-acre-foot irrigation reservoir that is impounded by the dam.

SEMA, of Englewood, Colo., is to: excavate the embankment and toe drain, construct a filter/drainage blanket, place geonet composite on the excavated face of the embankment, construct a two-stage sand filter and coarse sand drain system, place geotextile on the drain, construct a downstream stability berm, construct a two-stage filter drain in the channel and slopes downstream of the spillway and outlet works stilling basin, repair portions of the upstream dam face, and construct a toe drain system with monitoring wells.

Reclamation estimates the rehabilitation will create more than 160 direct and indirect jobs for a year.

Minidoka Dam, Idaho

Reclamation has awarded a $21.32 million contract to Record Steel and Construction Inc. to construct spillways and canal headworks to rehabilitate 27.7-MW Minidoka Dam on the Snake River in Idaho.

Reclamation issued a record of decision in September 2010 calling for replacement of a spillway and canal headworks cited in an environmental impact statement for Minidoka Dam.

Minidoka is an 86-foot-tall zoned earthfill structure that began operating in 1909. Reclamation said concrete of the 2,237-foot-long wood and concrete spillway, stoplog structure piers, and canal headworks has deteriorated to the point where it could fail soon. In addition, the headworks for the canals that run on the north and south sides of the dam show visible signs of deterioration.

Record Steel, of Meridian, Idaho, is to furnish and construct a new south gated spillway, north and south roller-compacted-concrete dikes, north and south side canal headworks, and north and south RCC overflow spillways. Work also includes modifications to the existing north gated spillway.

Echo Dam, Utah

Reclamation has awarded an $18.4 million contract to PNK Constructors LLC for dam safety excavation work at Utah’s 4.5-MW Echo Dam.

Operated by the Weber River Water Users Association, Echo Dam is a 158-foot-tall zoned earthfill structure that was constructed between 1927 and 1931 as part of the Weber River Project to help supply irrigation water to 109,000 acres west of the Wasatch Mountains. Reclamation awarded a $1.3 million contract in May to Foothill Engineering and Dewatering Inc. of California to dewater the work site to enable excavation for the dam safety work.

Reclamation announced Aug. 26 that PNK Constructors, of Coalville, Utah, is to perform major excavation on the downstream side of the dam to replace potentially liquefiable materials in the dam foundation with stronger and denser material. A large stability berm is to be built on the downstream side of the dam while the crest is to be raised 3 feet. A second stability berm will be added on the upstream side of the dam.

The work is to be performed between October 2011 and winter 2013.

A second contract to modify the spillway is to be awarded in September 2012, with the entire seismic modification project to be completed by the end of 2014.

TVA upgrades warning systems at 12 dams

The Tennessee Valley Authority has installed a new warning system at its 60-MW Watauga Dam and modified systems at 11 other dams, to improve public safety during water releases from the dams.

The system at Watauga Dam, which began operating in September 2011, includes signs, warning horns and strobe lights to alert the public to water discharges that can cause a rapid rise in water levels below the dam. The warning horns will not be used at night, to aviod disturbing nearby residents.

Modifications to the warning systems at the 11 other dams, completed in October 2011, involve activating only strobe light warning systems at night before water level changes. New signs will inform the public that warning sirens or horns will not be used at night. The dams affected are 76-MW Appalachia, 10-MW Blue Ridge, 136-MW Cherokee, 136-MW Douglas, 36-MW Fort Patrick Henry, 32-MW Great Falls, 100-MW Norris, 24-MW Ocoee No. 1, 40-MW South Holston, 40-MW Tims Ford and 11-MW Wilbur.

TVA operates 29 dams with hydroelectric facilities. The warning systems at TVA’s other eight tributary dams and its nine dams on the Tennessee River will not change, says John McCormick, senior vice president of river operations with TVA.

Corps awards multiple dam repair contracts

The U.S. Army Corps of Engineers has awarded three contracts worth a total of more than $47 million for dam safety work in two states and on the national level.

Canton Lake Dam, Oklahoma

The Corps has awarded a $37.57 million contract to ASI Constructors Inc. for construction of a concrete weir and hydraulic structures as part of an auxiliary spillway at Canton Lake Dam on the North Canadian River in Oklahoma.

Canton Dam, a 68-foot-tall, 15,140-foot-long earthfill embankment, includes a 778-foot-wide service spillway at the right abutment with 16 tainter gates. Corps hydraulic studies found the existing spillway is unable to discharge a probable maximum flood and the dam is likely to fail during a major flood.

To address the inadequate spillway capacity, the Corps has begun construction of an auxiliary spillway at the right abutment. Under a previous contract, a 480-foot-wide auxiliary channel has been partially excavated. Fifty-foot-tall vertical diaphragm walls line the channel. The Corps chose a Fusegate system from Hydroplus Inc. for the new spillway.

ASI Constructors, of Pueblo West, Colo., is to place a concrete weir about 35 feet deep and 70 feet long spanning the width of the channel. Other work includes a 40-foot-tall water intake monolith with a 47- by 15-foot base; 250 feet of 11-foot-diameter conduit; 30-foot-tall, 50-foot-wide Fusegates; diaphragm walls with anchors; and stop-log manufacture.

Old Hickory Dam, Tennessee

The Corps has awarded a contract to Bluegrass Contracting Corp. to perform bluff stabilization at the 100-MW Old Hickory hydro project on the Cumberland River in Tennessee.

The dam requires work to stabilize the right abutment bluff by placing reinforced shotcrete in three separate areas.

Bluegrass Contracting, of Lexington, Ky., received a $613,485 contract for the bluff stabilization, which includes scaling the rock bluffs in order to remove overhangs and irregularities. The contractor is to install rock dowels, wire mesh reinforcement, and fiber-reinforced shotcrete.

Dam safety program

The Corps has awarded a $9.5 million contract to URS Group Inc. for risk management support to the National Dam Safety Program, National Levee Safety Program and the Corps’ Risk Management Center.

URS, of Dallas, is to provide risk management support within the Tulsa District’s area of responsibility and in other districts and centers nationwide as required to support the safety programs and the Risk Management Center.

Work is to include risk analysis in support of issue evaluation studies, dam safety modification studies, and construction activities.

Two dams weather high water levels from Hurricane Irene

Gilboa Dam, which endured record high water levels created by Hurricane Irene, suffered no damage and is structurally sound, according to a full engineering inspection by the New York City Department of Environmental Inspection. At its peak, the water level was 1.5 feet higher than the previous record set in January 1996, according to city officials.

And New York Power Authority is monitoring the status of an earthen embankment dam that began leaking at the 11.8-MW Vischer Ferry project on the Mohawk River. The embankment began leaking in late August as a result of historic high river flows from Hurricane Irene. NYPA engineers fortified the structure, built in 1912 as part of the Erie Canal, using a combination of sand, gravel and roadbed material.

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